1. Field of the Invention
This invention relates to a taking lens system suitable for an inexpensive, fixed-focus camera and a photographic camera equipped with the taking lens system.
2. Description of Related Art
A considerably various types of photographic cameras for a wide variety of purposes and, in recent years, various types of lens-fitted film units which bring about easy pleasure in taking pictures have been put on the market. Such a lens-fitted film unit incorporates a roll of film contained in a cartridge which is installed in a case equipped with an exposure mechanism including a taking lens and a shutter. The lens-fitted film unit is widely spread because of the convenience that it can be gotten whenever and anywhere wishing to take pictures and is put to a photo-shop as it is after all exposures thereof. Further, the lens-fitted film unit is made with a simple structure because it has one of its great importance to be cheap and is under the necessity of being manufactured at costs as low as possible. For example, a taking lens comprising a single lens element is held in position by a lens holder formed with a fixed diameter of aperture stop and a fixed focal length standard to most objects. The film in the lens-fitted film unit is of a 35 mm type of roll film which has a picture format 24.times.36 mm.
Most taking lenses for these lens-fitted film units are featured by a focal length between 32 and 35 mm, an F-number of 9.5 and a half angle of view of approximately 34.degree. and made of plastic materials, which is always desirable for manufacturing costs and production on a large scale. Because the use of plastic materials imposes a restraint on optical performance, such as a refraction power, of the taking lenses, under the condition that the taking lens has a focal length remaining constant, it is hard to make a Petzval sum dictating curvature of field of the taking lens smaller. For this reason, in order for the lens-fitted film unit to remove or significantly reduce curvature of field which is sufficiently corrected by the taking lens, a film support for supporting and guiding a film surface in the exposure position is curved according to the curvature of field.
In recent years, a new type of film cartridge or film patrone has been placed on the market. This new type of film cartridge has a feature of unwinding a film strip from a cartridge spool and sending out the film strip out of the film cartridge by turning the cartridge spool. The film strip in the film cartridge has a width of 24 mm and a picture format or image frame of 16.7.times.30.2 mm which is smaller than that of the conventional 35 mm type roll film. On the other hand, there have been widely spread a full-frame 35 mm type of camera and lens-fitted film unit designed and adapted to take pictures of a panoramic format of 13.times.36 mm as well as 35 mm full-size format pictures.
If providing prints which are the same in full format or panoramic format as prints from the conventional 35 mm format film, the prints must be enlarged at magnifications larger than conventional prints. Accordingly a miniaturized image frame or picture format causes a demand for high optical performance of a taking lens. Further, in order for a taking lens to provide a desirable panoramic effect, the taking lens is necessary to have a wide angle of view. These lens demands are apt to make it difficult to design inexpensive taking lenses. Accordingly, in order for lens-fitted lens units containing the new format of film roll to have an angle of view and optical performance at the same level as those of two component taking lenses.
A two component taking lens needs mechanical elements such as a lens holder, a fixture ring and a light blocking member as many as the number of lens elements assembled together with the lens elements, which always makes a structure complicate and needs precise assembling work in addition to a rise in production costs.